Drive mechanism having improved locking means



Dec. 1, 1970 G. D. FREDELL ,5

DRIVE MECHAAI'IISM HAVING IMPRCVED LOCKING MEANS Filed Jan. 9, 1969 FIG.3

B I0 54 I 52 6O 42 58V 40 l 54 '30 f I 77/ 38 O --32 34 v I s INVENTOR. GARY D. FREDELL ATTORNEYS.

3,543,596 DRIVE MECHANISM HAVING IMPROVED LOCKING MEANS Gary D. Fredell, East Moline, 1",, assignor, by mesne assignmentss, to Gulf Western Industries, New York, N.Y., a corporation of Delaware Filed Jan. 9, 1969, Ser. No. 790,018 Int. Cl. F16h 27/04 U.S. Cl. 74--128 Claims ABSTRACT OF THE DISCLOSURE A drive mechanism for converting linear motion to rotary motion including a shaft rotatably mounted on a frame, a ratchet wheel secured to the shaft for rotation therewith in a forward and reverse direction, drive means for reciprocating a drive pawl between an uppermost position and a lowermost position, the pawl adapted to reciprocate into and out of engagement with the ratchet wheel to drive the wheel in a forward direction, and a lock pawl pivotally supported on the frame and biased into contact with the ratchet wheel to prevent rotation of the wheel in the reverse direction. There is further provided an improved locking means which is mounted on the drive means and reciprocates therewith to prevent rotation of the ratchet wheel in the forward direction when the drive pawl is traveling downward from a predetermined position, intermediate the uppermost and lowermost positions, to the lowermost position.

DISCLOSURE This invention is directed to the drive mechanism art, and more particularly to a mechanism in which reciprocating linear motion is converted to rotary motion.

The invention is particularly applicable to stepping switches for sequence control and will be described with particular reference thereto, although it will be appreciated that the invention has broader application and may be used whenever it is desired to achieve step-bystep motion.

A great number of prior art mechanisms have been developed in which reciprocating linear motion is converted to rotary motion. One type of such prior art mechanism employs a ratchet wheel on a shaft, a pawl which is adapted to engage the teeth on the ratchet Wheel and some appropriate mechanism to reciprocate the pawl into and out of engagement with the ratchet teeth. The path of reciprocation of the pawl is normally tangential to the ratchet wheel and as the pawl approaches the ratchet wheel it engages a ratchet tooth and rotates the ratchet wheel and shaft a predetermined amount in a forward direction. One advantage of a mechanism such as this is that a predetermined incremental rotation may be imparted with a relatively simple device.

The prior art has also devised means to prevent unwanted rotation of the ratchet wheel in a reverse direction. Typically, the prior art approach has employed some form of a locking detent or pawl which engages the ratchet wheel to prevent reverse rotation of the wheel. These locking detents or pawls are normally biased in some manner into continuous engagement with the teeth of the ratchet wheel but are permitted to ratchet over the teeth as the ratchet wheel is rotated by the drive pawl in the forward direction. As the drive pawl is returned to an uppermost position to pick up the next tooth on the ratchet wheel, the locking detent or pawl remains in engagement with the teeth of the ratchet wheel and precludes rotation of the wheel in the reverse direction. Prior art devices have also included an additional locking means for preventing rotation of the ratchet wheel in the United States Patent 0 Patented Dec, 1, 1970 forward direction when the drive pawl is in various positions.

Mechanisms such as those here and above described have some short comings. Thus, although the prior art has provided means for preventing rotation of the ratchet wheel in both the reverse and forward directions, the structural components necessary to prevent rotation in the forward direction have proven to be quite complicated and required numerous parts. Thus, it has been necessary in prior art devices to include locking bars, guide means and other miscellaneous supporting structure. Although such devices are operative, the large number of components has proved undesirable. Furthermore high manufacturing costs have been associated with such devices in view of the many parts necessary for their successful operation.

In accordance with the present invention there is provided an apparatus for converting linear motion to rotary motion including a shaft rotatably mounted on a frame, a ratchet wheel secured to the shaft for rotation therewith in a forward and reverse direction, drive means for reciprocating a drive pawl between an uppermost position and a lowermost position, the pawl adapted to reciprocate into and out of engagement with the ratchet wheel to drive the wheel in a forward direction, and a lock pawl pivotally supported on the frame and biased into contact with the ratchet wheel to prevent rotation of the wheel in the reverse direction. There is further provided an improved locking means which is mounted on the drive means and reciprocates therewith to prevent rotation of the ratchet wheel in the forward direction when the drive pawl is traveling downward from a predetermined position, intermediate the uppermost and lowermost positions, to the lowermost position.

The principal object of the present invention is to provide a drive mechanism in which reciprocating linear motion is converted into rotary motion.

It is a further object of the present invention to provide a drive mechanism in which the rotary motion of a shaft is controlled in both a forward and reverse direction.

Another object of the invention is to provide a drive mechanism in which the ratchet wheel may not rotate more than a predetermined amount in the forward direction with each actuation of the mechanism.

A still further object of the invention is to provide a drive mechanism which is simple, economical and requires a minimum amount of parts to achieve the desired mode of operation.

The invention may take physical form in certain parts and arrangements of parts, a preferred embodiment which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof and wherein;

FIG. 1 is a plan view of the preferred embodiment of drive means;

FIG. 2' is a cross sectional view of the drive mechanism taken along line 22 of FIG. 1 showing the drive pawl in its uppermost position; and

FIG. 3 is a cross sectional view of the drive mechanism taken along line 2-2 of FIG. 1 showing the drive pawl in the lowermost position.

Referring now to the drawings wherein the showings are for the purpose of illustrating the preferred embodiment of the invention only and not for the purpose of limiting same, FIG. 1 shows the overall arrangement of a drive mechanism, indicated generally by the reference letter A, supported on a frame B which may be mounted on a suitable supporting structure (not shown).

Referring now to FIGS. l-3, the frame B is comprised of a pair of side walls 10, and a bottom wall 12. A shaft 14 is rotatably supported by bearings 16 which are disposed in each of the side walls 10. The longitudinal relationship of the shaft 14, relative to the bearings 16, is maintained by clips 18. One end of the shaft 14 extends outward beyond the side wall and may carry on this end an appropriate driving element, such as a gear 20. Secured to the shaft 14 for rotation therewith, and in termediate the side walls 10, is a ratchet wheel 22 having formed on its periphery a plurality of ratchet teeth 24.

Intermediate the shaft 14 and bottom wall 12, and substantially parallel thereto, is a plate 30 having two of its opposed edges supported by the side walls 10. Disposed within the area defined by the side walls 10, bottom wall 12 and plate 30 is a drive means. This drive means may take many forms, however in the preferred embodiment it is shown as a solenoid comprising a solenoid coil 32, and a solenoid actuated reciprocating plunger 34 adapted to reciprocate in a plane substantially perpendicular to the plate 30 and bottom wall 12. A bottom stop 36 provides a bottom limit for the reciprocation of the plunger 34. Furthermore, the plate 30 includes an aperture 38 through which the upper end of the plunger 34 projects.

An upwardly opening recess or bore 40 is provided in the upper end of the plunger 34 to receive therein a drive pawl 42 having upper most and lowermost positions. A pin 44 pivotally supports the drive pawl 42 in the recess 40, to permit the pawl to pivot toward and away from the ratchet wheel 22. Stop means for limiting the pivotal movement of the drive pawl 42 away from the ratchet wheel 22 is provided. Th stop means may take many forms, however, in the preferred embodiment it is shown as a fiat surface 50 formed on the lower end of the drive pawl 42.

The drive pawl 42 is defined by substantially parallel inner and outer opposed faces, the inner face being ad jacent the ratchet wheel 22. A beveled surface 52 formed on the upper extremity of the drive pawl 42 defining a nose 54 is adapted to engage the ratchet teeth 24 in the manner shown in FIG. 3. The inner face of the drive pawl 42 defines a step-like configuration having a locking surface 56 for lockingly engaging the ratchet teeth 24 (as best shown in FIG. 2) to prevent rotation of the ratchet wheel 22 in the forward direction when the drive pawl is traveling downward from the upper most position to a predetermined position, intermediate the uppermost and lowermost positions. First means for biasing the drive pawl 42 toward the ratchet wheel 22 is provided. The first biasing means may take many forms, however, in the preferred embodiment it is illustrated as a spring 58 coaxially disposed about pin 44 having its end portions in contact with the drive pawl 42 and recess 40 respectively. As will be understood by those skilled in the art to which this invention pertains, reciprocation of the plunger 34 will cause the drive pawl 42 to be reciprocated therewith, and as the pawl engages the ratchet teeth 24 on the ratchet wheel 22, a rotary motion in the forward direction will be imparted to the shaft 14.

In many applications it is desirable to assure that the ratchet wheel 22 is advanced only a predetermined amount in the forward direction with each actuation of the mechanism. Moreover, it is also often desirable to prevent reverse rotation of the ratchet wheel 22.

To accomplish the first of these purposes, there is provided a locking means, indicated generally by the reference numeral 60, which is disposed on the upper end of the plunger 34 to reciprocate therewith. The locking means includes an annular base 62, which is coaxially supported by the plunger 34, having an upwardly extending generally L-shaped locking arm 64. The locking arm 64 terminates in a locking face 66 adapted to engage the ratchet teeth 24 in the manner shown in FIG. 3; thereby assuring that the ratchet wheel 22 is advanced only a predetermined amount in the forward direction with each actuation of the mechanism. Second means for biasing the drive pawl 42, and hence the plunger 34 and locking means 60, toward the upper most position is provided. The second biasing means may take many forms, however, in the preferred embodiment it is shown as a spring 68 disposed intermediate the plate 30 and the annular base 62 of the locking means 60.

T o accomplish the second of these purposes, there is provided a lock pawl 74 (as shown in FIG. 1) which is pivotally mounted on a shaft 76 supported by the frame B. The lock pawl 74 is retained on the shaft 76 by a locking clip 78 and normally biased by a spring 80 toward the ratchet wheel 22. The lock pawl 74 includes a nose portion 82 which is adapted to engage the ratchet teeth 24 at all times to prevent reverse rotation of the shaft 14, but will ratchet over the teeth as the ratchet wheel 22 is rotated in the forward direction by the drive pawl 42.

The operation of the above-described mechanism will now be explained in greater detail.

With the components of the mechanism in the uppermost position, as shown in FIG. 2, it will be appreciated that the shaft 14 is effectively restrained from any rotation. Thus, any tendency of the shaft 14 to rotate in the reverse direction will be restrained by the lock pawl 74 which is engaged with the ratchet teeth 24 (see FIG. 1). Similarly, the locking surface 56 of the drive pawl 42 is also in engagement with the ratchet teeth 24 (see FIG. 2) to prevent rotation of the shaft 14 in the forward direction. Furthermore, the drive pawl 42 cannot be pivoted away from the ratchet wheel 22, thereby permitting forward rotation, because of the flat surface 50 on the drive pawl which maintains the requisite engagement.

When it is desired to impart rotation to the shaft 14, the solenoid coil 32 is energized thereby causing the plunger 34 to be drawn toward the bottom stop 36. As the plunger 34 is displaced downward, the locking surface 56 of the drive pawl 42 remains in engagement with the ratchet teeth 24 due to the fiat surface 50 thereby preventing the pawl from pivoting away from the ratchet wheel 22. The locking surface 56-to-ratchet-teeth 24 engagement continues until the drive pawl 42, in its downward travel, reaches a predetermined position intermediate the uppermost and lowermost positions. The predetermined position may be further defined by the operative fact that at this position the nose 54 of the drive pawl 42 becomes disengaged from one ratchet tooth 24 and is biased toward the shaft 14 by spring 58 to engage the next tooth on the ratchet wheel 22. In pivoting toward the shaft 14, the flat surface 50' on the drive pawl 42 is no longer in contact with the plunger 34. Hence, locking surface 56 can no longer prevent rotation of the shaft 14 in the forward direction. It can therefore be seen that the locking surface 56 prevents forward rotation of the shaft when the drive pawl 42 is traveling downward from the uppermost position to the predetermined position.

Upon reaching the predetermined position the locking face 66 of the locking arm 64 of locking means 60 engages the ratchet teeth 24 to prevent rotation of the shaft 14 in the forward direction. Thus, although the locking surface 56 of the drive pawl 42 is no longer able to perform this function, still forward shaft rotation is prevented by the locking means 60. The locking face 66 remains in engagement, thus preventing shaft rotation in the forward direction, until the drive pawl 42 reaches its lowermost position (as best shown in FIG. 3). The lowermost position is arrived at when the downward travel of the plunger 34 ceases due to its coming in contact with the bottom stop 36. It can therefore be seen that the locking means 60 prevents forward rotation of the shaft 14 when the drive pawl 42 is traveling downward from the predetermined position to the lowermost position.

When the solenoid coil 32 is de-energized, the spring 68 returns the plunger 34, drive pawl 42 and locking means 60 from the lowermost position, as shown in FIG. 3, to the uppermost position, as shown in FIG. 2.

As the plunger 34 travels upward, the drive pawl 42 picks up a different tooth 24 on the ratchet wheel 22 and imparts rotary motion to the shaft 14 in the forward direction. In traveling upward from the lowermost position, the locking means 60 is not in engagement with the ratchet teeth 24, thus the ratchet wheel 22 is free to rotate and drive the shaft 14 in the forward direction.

It will be appreciated that this mechanism prevents any rotation of the shaft 14 from external sources and limits the rotation of the shaft to a single ratchet tooth with each energization of the solenoid coil 32. The design of the mechanism assures that all steps in the cycle are positively controlled by either the drive pawl 42, the locking surface 56 of the drive pawl, the locking means 60 or the lock pawl 74, or combinations thereof. Thus, rotation of the shaft 14 is fully controlled in both direction and amount at all times.

Having thus defined the invention, I claim:

1. In an apparatus for converting linear motion to rotary motion including a shaft rotatably mounted on a frame, a ratchet wheel secured to said shaft for rotation therewith; drive means for reciprocating a drive pawl between uppermost position and a lowermost position, said pawl adapted to reciprocate into and out of engagement with said ratchet wheel to drive said wheel in a forward direction, and a lock pawl pivotally supported on said frame and biased to be in contact .with said ratchet wheel to prevent rotation of said wheel in a reverse direction; the improvement comprising: locking means mounted on said drive means for reciprocation therewith to prevent rotation of said ratchet wheel in the forward direction when said drive pawl is out of driving engagement with said ratchet wheel and traveling downward from a predetermined position, intermediate the uppermost and lowermost positions, to the lowermost position.

2. The apparatus defined in claim 1, wherein said drive pawl has a locking surface configured to prevent rotation of said ratchet wheel in the forward direction when said drive pawl is traveling downward from the uppermost position to the predetermined position.

3. The apparatus defined in claim 1, wherein said drive means comprises a solenoid actuated reciprocating plunger having a recess in its upper end in which is pivotally supported said drive pawl, first means for biasing said drive pawl toward said ratchet wheel, second means for biasing said drive pawl toward its uppermost position.

4. The apparatus defined in claim 3, including stop means carried by said drive pawl for limiting the pivotal movement of said pawl away from said ratchet wheel.

5. The apparatus defined in claim 3, wherein said locking means comprises a base supported on the upper end of said plunger and a locking arm projecting upward from said base, said locking arm configured to provide engagement with said ratchet wheel when said drive pawl is traveling downward from the predetermined position to the lowermost position, whereby said wheel is prevented from rotating in the forward direction.

References Cited UNITED STATES PATENTS 2,323,235 6/1943 Nordenswan 74142 2,900,840 8/1959 Greve 74-575 2,924,107 2/1960 Fresard et al 74--126 2,990,723 7/1961 Holpuch 74-575 3,148,815 9/1964 Jung 74126 WESLEY RATLlFF, JR., Primary Examiner 

